The Computational Core will support the work of the center by calculating the properties and reactivities of models for metal oxide ultrafine particles (UFPs) and fine particles (FPs) suggested by experiment. The models of UFPs will include up to 20 metal atoms and a varying number of oxygen atoms. Reactions of these models with chlorinated benzenes and phenols to form environmentally persistent free radicals (EPFRs) and dioxins will be studied. The goal will be to provide a more complete understanding of the experimental results by identifying particularly important cluster geometries and sites on these clusters for comparison with the results for larger particles. The Core will utilize the computational facilities available at Louisiana State University and within the State of Louisiana. Louisiana State University's High Performance Computing group maintains approximately 21.5 TFIops of computing power spread over approximately 2000 cores. The Louisiana Optical Network Initiative's computing facilities provide approximately 45 TFIops of computing power spread over approximately 6000 cores. Standard software is available on these computers including Gaussian, GAMESS, NWChem, Wein, Charmm, CPMD, Gromacs, NAMD, PINY-MD, and VMD. The bulk of the computational support will use the ab initio programs Gaussian09 and CPMD, which can perform first principles calculations. Density functional calculations will use the aug-cc-pVDZ and LANL2DZ basis and selected functionals. Gaussian09 includes the MOB functional of Truhlar, which is optimized for use with transition metals. This functional, along with B3LYP and other selected hybrid functionals, will be used to optimize the geometric structures of metal oxide clusters and metal oxide-EPFR complexes. The calculated atomization and ionization energies, the electron affinities, and the charge and spin densities will be used to characterize the clusters of copper and iron oxides. The EPFR-cluster complexes formed by reaction with 2-monochlorophenol and 1,2-dichlorobenzene will be determined. The AEs of reaction, selected activation energies, and vibrational frequencies will be compared with experiment. Metal oxide clusters will be optimized for different spin states in order to determine the lowest energy spin state.